Before the U.S. housing bubble burst, there was an implicit widespread belief that home prices could never fall. Lenders and borrowers both believed this, and it's this mentality that helped fuel the bubble.

"In the latest Zillow Home Price Expectations Survey released Feb. 12, over 100 experts predicted moderated appreciation in future home values, closer to the pre-bubble norms of 3 to 5 percent per year," said Zillow's Meredith Miller. "On average, the panel predicted national appreciation of 4.5 percent through the fourth quarter of 2014. Over the same period, the Zillow Home Value Forecast predicts 4.8 percent appreciation nationwide. Over a longer term, the panel predicted a cumulative change in home values of 19.7 percent through the end of 2018, on average."

That's all well and good. But it's worth noting that the most pessimistic quartile of those surveyed also see prices going up. It's a modest amount, but they see prices going up a cumulative 10.9% through 2018. That's a 2.1% rate annualized.

Should we be worried that almost no one sees prices falling?

The good news is that all of these home price bulls don't see prices accelerating to bubble-era rates.

"On an annual basis, the panelists predicted home value appreciation to slow to 3.8 percent in 2015 and 3.3 percent by 2018," said Miller. "Overall, the panel predicted an average annual pace of 3.7 percent appreciation for the next five years. These rates of appreciation are much more in line with pre-housing bubble appreciation rates averaging 3.6 percent annually from 1987 to 1999, compared to the average of 7 percent annual appreciation rate experienced from 2000 to 2007."

Still, it makes us a little uncomfortable to see so few worried about falling prices. It's this type of attitude that eventually leads to price bubbles.